[Does daily hemodialysis influence urea kinetic modeling (UKM) coefficients?--Preliminary report]

Large number of data shows beneficial effects of implementing daily hemodialysis (DH) upon the outcome in patients dialysed previously in 3 times a week hemodialysis (3H) schedule. The mechanisms responsible for this phenomenon are still unclear, despite the time of low-flux DH sessions is shortened almost by half. Evaluation of the effect of doubling the number of hemodialyses per week upon so called cellular clearance (intercompartmental diffusion coefficient, Kc) computed in 2 pool-model was main aim of this study. 6 chronically dialysed patients (previously 3x per week) were subjected to DH. Based upon output data from UKM and weekly KT/V, the time for each DH session was computed, with no change in Kd (dialyser clearance). Kc was estimated from double-pool volume variable model equations and rebound. By the use of almost similar dialyser clearances in 16 conventional and 29 DH modeling sessions, estimated Kc values had been found non significantly higher in DH: (323.16; S.D. 187.86 vs. 268.80; S.D. 104.09 ml/min; p=0,68). Mean ultrafiltration/pre-dialysis body weight ratio (UFR/BW1) was 4,97 (S.D. 2.27)% in conventional hemodialysis and 3.66 (S.D. 1.46)% in DH. Mean dialysis index Kt/V values had decreased in DH (0.79; S.D. 0.17, vs. 1,34 (S.D. 0.26). Mean UFR/W1 ratio correlated negatively with Kc either in conventional or in DH (r=-0.653; p = 0.006 and r=-0.552; p=0.0036, respectively). Statistically significant negative correlation between Kt/V and Kc was found only in DH subjects (r=-0.466, p =0.010). The authors concluded, that increased Kc observed in patients subjected to DH may be responsible for better dialysis efficacy in patients switched into this treatment modality.